Reproductive and Hormonal Function of the Male

Question 1

The three major subdivisions of the male reproductive functions

Answer 1

1. Spermatogenesis, which means the formation of sperm
2. Performance of the male sexual act
3. Regulation of male reproductive functions by the various hormones.

Question 2

Physiological Anatomy of the Male

Sexual Organs

Answer 2

The testis is composed of up to 900 coiled seminiferous tubules, each averaging more than one-half meter long, in which the sperm are formed.

The sperm then empty into the epididymis, which is another coiled tube about 6 meters long.

The epididymis leads into the vas deferens, which enlarges into the ampulla of the vas deferens immediately before the vas enters the body of the
prostate gland.

Two seminal vesicles, empty into the prostatic end of the ampulla, and the contents pass into an ejaculatory duct leading through the body of the
prostate gland and then emptying into the internal urethra.

Prostatic ducts (part of the ejaculatory duct that runs through the prostate gland)also empty from the prostate gland into the ejaculatory duct and
from there into the prostatic urethra.

The urethra is the last connecting link from the testis to the exterior. The urethra receives mucus derived from a large number of minute urethral
glands located along its entire extent and even more so from bilateral bulbourethral glands (Cowper glands) located near the origin of the urethra.

Question 3

When does Spermatogenesis occur

Answer 3

During embryonic development, the primordial germ cells migrate into the
testes and become immature germ cells
called spermatogonia, which lie in two or
three layers of the inner surfaces of the
seminiferous tubules.

At puberty the spermatogonia begin to
undergo mitotic division and continually
proliferate and differentiate through
definite stages of development to form
sperm.

Question 4

Stages in
the development of sperm from spermatogonia
Steps in Spermatogenesis

Answer 4

Spermatogenesis occurs in the seminiferous tubules during active sexual life as the result of stimulation by anterior pituitary gonadotropic hormones.

Spermatogenesis begins at an average age of 13 years (puberty) and continues throughout most of the remainder of life but decreases markedly in
old age.

In the first stage of spermatogenesis, the spermatogonia migrate among
Sertoli cells toward the central lumen of the seminiferous tubule

Spermatogonia that cross the barrier into the Sertoli cell layer become
progressively modified and enlarged to form large primary spermatocytes

These primary spermatocytes, in turn, undergoes meiotic division to form two secondary spermatocytes. After another few days, these secondary
spermatocytes also divide to form spermatids that are eventually modified to
become spermatozoa (sperm).

Question 5

Meiosis

Answer 5

During the change from the
spermatocyte stage to the spermatid
stage, the 46 chromosomes (23 pairs
of chromosomes) of the spermatocyte are divided, and thus 23 chromosomes go to one spermatid
and the other 23 go to the second
spermatid.

The entire period of spermatogenesis,
from spermatogonia to spermatozoa,
takes about 74 days.

Question 6

Sex Chromosome

Answer 6

In each spermatogonium, one of the 23 pairs of chromosomes carries the genetic information that determines the sex of each eventual offspring.

This pair (XY) is composed of one X chromosome, which is called the
female chromosome, and one Y chromosome, the male chromosome.

During meiotic division, the male Y chromosome goes to one spermatid that then becomes a male sperm, and the female X chromosome goes to
another spermatid that becomes a female sperm.

The sex of the eventual
offspring is determined by which of these two types of sperm fertilizes the
ovum.

Question 7

Sperm structure

Answer 7

Each spermatozoon is composed of a head and a tail.

The head comprises the condensed nucleus of the cell, with only a thin cytoplasmic and cell membrane layer around its surface.

On the outside of the anterior two thirds of the head is a thick cap called
the acrosome that is formed mainly from the Golgi apparatus.

The acrosome contains several enzymes similar to those found in lysosomes
of the typical cell, including hyaluronidase (which can digest proteoglycan
filaments of tissues) and powerful proteolytic enzymes (which can digest
proteins).

These enzymes play important roles in allowing the sperm to enter the ovum
and fertilize it.

Question 8

Structure of the human spermatozoon.

Answer 8

The tail of the sperm, called the
flagellum, has three major components:

1. A central skeleton constructed
   of 11 microtubules, collectively
   called the axoneme.
2. A thin cell membrane covering
   the axoneme; and
3. A collection of mitochondria surrounding the axoneme in the proximal portion of the tail (called
   the body of the tail ).

Back-and-forth movement of the tail provides motility for the sperm.

The energy for this process is supplied in the form of ATP, which is synthesized by the mitochondria in
the body of the tail.

Question 9

Hormonal Factors That Stimulate

Spermatogenesis

Answer 9

Testosterone

Luteinizing Hormone

Follicle Stimulating Hormone

Estrogen

Growth Hormone

Question 10

Testosterone

Answer 10

Secreted by the Leydig cells located in the interstitium of the testis, is essential for growth and division of the testicular germinal cells, which is the first stage in forming sperm.

Question 11

Luteinizing Hormone

Answer 11

Secreted by the anterior pituitary gland, stimulates the Leydig cells to secrete testosterone

Question 12

Follicle-Stimulating Hormone

Answer 12

Also secreted by the anterior pituitary gland,stimulates the Sertoli cells, without this stimulation, the conversion of spermatids to sperms(Process of spermatogenesis) will not occur

Question 13

Estrogen

Answer 13

Formed from testosterone by the Sertoli cells when they are
stimulated by follicle-stimulating hormone, are probably also essential for
spermiogenesis.

Question 14

Growth hormone

Answer 14

Specifically promotes early division of the spermatogonia
themselves; in its absence spermatogenesis is severely deficient or absent,
thus causing infertility.

Question 15

Storage of Sperm in the Epididymis

Answer 15

After formation in the seminiferous tubules, the sperm require several days to pass through the 6-meter-long tubule of the epididymis.

Sperm removed from the seminiferous tubules and from the early portions
of the epididymis are non-motile and cannot fertilize an ovum.

However, after the sperm have been in the epididymis for 18 to 24 hours, they develop the capability of motility, even though several inhibitory
proteins in the epididymal fluid still prevent final motility until after ejaculation.

They can remain stored in the epididymis, for at least a month. During this time, they are kept in a deeply suppressed, inactive state.

However, with a high level of sexual activity and ejaculations, they may be stored no longer than a few days.

Question 16

Function of the Seminal Vesicles

Answer 16

 Each seminal vesicle secretes a mucoid material containing an abundance
of fructose, citric acid, and other nutrient substances, as well as large
quantities of prostaglandins and fibrinogen. Prostaglandins are believed to aid fertilization in two ways:
(1) reacting with the female cervical mucus to make it more receptive to sperm
movement and
(2) by possibly causing backward, reverse peristaltic contractions in the uterus
and fallopian tubes to move the ejaculated sperm toward the ovaries (a few
sperm reach the upper ends of the fallopian tubes within 5 minutes).
 During the process of emission and ejaculation, each seminal vesicle empties
its contents into the ejaculatory duct shortly after the vas deferens empties
the sperm.
 This action adds greatly to the bulk of the ejaculated semen, and the fructose
and other substances in the seminal fluid are of considerable nutrient value
for the ejaculated sperm until one of the sperm fertilizes the ovum.

Question 17

Life span of ejaculated sperm

Answer 17

The normal motile, fertile sperm are capable of flagellated movement through the fluid medium at velocities of 1 to 4 mm/min.

The activity of sperm is greatly enhanced in a neutral and slightly alkaline medium, as exists in the ejaculated semen, but it is greatly depressed in a
mildly acidic medium.

A strong acidic medium can cause the rapid death of sperm.

The activity of sperm increases markedly with increasing temperature, but
so does the rate of metabolism, causing the life of the sperm to be considerably shortened.

Although sperm can live for many weeks in the suppressed state in the genital ducts of the testes, the life expectancy of ejaculated sperm in the
female genital tract is only 1 to 2 days.

Question 18

Function of the Seminal Vesicles

Answer 18

Each seminal vesicle secretes a mucoid material containing an abundance of fructose, citric acid, and other nutrient substances, as well as large
quantities of prostaglandins and fibrinogen.

Prostaglandins are believed to aid fertilization in two ways:

1. Reacting with the female cervical mucus to make it more receptive to sperm movement and
2. Possibly causing backward, reverse peristaltic contractions in the uterus and fallopian tubes to move the ejaculated sperm toward the ovaries (a few
   sperm reach the upper ends of the fallopian tubes within 5 minutes).

During the process of emission and ejaculation, each seminal vesicle empties its contents into the ejaculatory duct shortly after the vas deferens empties
the sperm.

This action adds greatly to the bulk of the ejaculated semen, and the fructose and other substances in the seminal fluid are of considerable nutrient value
for the ejaculated sperm until one of the sperm fertilizes the ovum.

Question 19

Function of the Prostate Gland

Answer 19

The prostate gland secretes a thin, milky fluid that contains calcium, citrate ion, phosphate ion, a clotting enzyme, and a profibrinolysin.

The slightly alkaline characteristic of the prostatic fluid may be quite important for successful fertilization of the ovum because the fluid of the vas
deferens is relatively acidic due to citric acid and metabolic end products of the sperm, inhibiting sperm fertility.

Also, the vaginal secretions of the female are acidic (with a pH of 3.5 to 4.0). Sperm do not become optimally motile until the pH of the surrounding
fluids rises to about 6.0 to 6.5.

Consequently, it is probable that the slightly alkaline prostatic fluid helps neutralize the acidity of the other seminal fluids during ejaculation and thus
enhances the motility and fertility of the sperm.

Question 20

Semen

Answer 20

Semen, is composed of the fluid and sperm from the vas deferens (about 10 percent of the total), fluid from the seminal vesicles (almost 60 percent), fluid from the prostate gland (about 30 percent), and small amounts from the mucous glands, especially the
bulbourethral glands.

The bulk of the semen is seminal vesicle fluid, which is the last to be ejaculated and
serves to wash the sperm through the ejaculatory duct and urethra.

The average pH of the combined semen is about 7.5, with the alkaline prostatic fluid
having more than neutralized the mild acidity of the other portions of the semen.

The prostatic fluid gives the semen a milky appearance, and fluid from the seminal
vesicles and mucous glands gives the semen a mucoid consistency.

Also, a clotting enzyme from the prostatic fluid causes the fibrinogen of the seminal vesicle fluid to form a weak fibrin coagulum that holds the semen in the deeper regions of the vagina where the uterine cervix lies.

In the early minutes after ejaculation, the sperm remain relatively immobile, possibly because of the viscosity of the coagulum. As the coagulum dissolves, the sperm
simultaneously become highly motile.

Once sperm are ejaculated in the semen, their maximal life span is only 24 to 48 hours at body temperature.

At lowered temperatures, however, semen can be stored for several weeks, and when frozen at temperatures below −100°C, sperm have been preserved for years.

Question 21

“Capacitation” of Spermatozoa Is Required

for Fertilization of the Ovum

Answer 21

Although spermatozoa are said to be “mature” when they leave the epididymis, their activity is held in check by multiple inhibitory factors
secreted by the genital duct epithelia.

Therefore, when they are first expelled in the semen, they are unable to fertilize the ovum.

However, on coming in contact with the fluids of the female genital tract, multiple changes occur that activate the sperm for the final processes of
fertilization.

These collective changes are called capacitation of the spermatozoa, which normally requires from 1 to 10 hours.

Question 22

“Capacitation” of Spermatozoa:

The changes which are associated with Capacitation

Answer 22

1. The uterine and fallopian tube fluids removes the various inhibitory factors that suppress sperm activity in the male genital ducts.
2. While the spermatozoa remain in the male genital ducts, they are continually exposed to large amounts of cholesterol. This cholesterol toughens the membrane of the acrosome preventing release of its
   enzymes. However, after ejaculation, the sperm lose much of their cholesterol causing the membrane at the acrosome becomes much weaker.
3. The membrane of the sperm becomes much more permeable to calcium ions, so calcium now enters the sperm and changes the activity of the flagellum, giving it a powerful whiplash motion in contrast to its previously weak undulating motion. In addition, calcium makes it possible for the acrosome to release its enzymes rapidly as the sperm penetrates the
   granulosa cell mass surrounding the ovum.

Thus, multiple changes occur during the process of capacitation. Without these changes, the sperm cannot make its way to the interior of the ovum
to cause fertilization.

Question 23

Acrosome Enzyme and Penetration of the

Ovum

Answer 23

Stored in the acrosome of the sperm are large quantities of hyaluronidase and proteolytic enzymes.

Hyaluronidase acts on the hyaluronic acid polymers in the intercellular cement that holds the ovarian granulosa cells together.

The proteolytic enzymes digest proteins in the structural elements of tissue cells that still adhere to the ovum.

Before a sperm can fertilize an ovum, it must dissolute the granulosa cell layers, and then it must penetrate through the thick covering of the ovum itself, the zona pellucida.

The sperm binds with receptor proteins in the zona pellucida.

The entire acrosome rapidly dissolves, releasing it’s enzymes. It is believed that the hyaluronidase among these enzymes is especially important in opening
pathways between the granulosa cells so that the sperm can reach the ovum.

Within another 30 minutes, the cell membranes of the sperm head and of the oocyte fuse with each other to form a single cell. At the same time, the genetic material of the sperm and the oocyte combine to form a completely new cell genome, containing equal numbers of chromosomes and genes
from mother and father.

This is the process of fertilization; the embryo then
begins to develop

Question 24

Male Sexual Act: Neuronal Stimulus for

Performance of the Male Sexual Act

Answer 24

The most important source of sensory nerve signals for initiating the male sexual act is the glans penis.

The glans contains an especially sensitive sensory end-organ system that transmits into the central nervous system of sensation called sexual
sensation.

The slippery massaging action of intercourse on the glans stimulates the sensory end organs, and the sexual signals in turn pass through the
pudendal nerve, then through the sacral plexus into the sacral portion of the spinal cord, and finally up the cord to undefined areas of the brain.

Areas adjacent to the penis may aid in stimulating the sexual act.

Stimulation of the anal epithelium, the scrotum, and perineal structures in general can send signals into the cord that add to the sexual sensation

Question 25

Psychic Element of Male Sexual Stimulation.

Answer 25

Appropriate psychic stimuli can greatly enhance the ability of a person to perform the sexual act. Simply thinking sexual thoughts or even dreaming that the act of intercourse is being performed can initiate the male act, culminating in ejaculation. Indeed, nocturnal emissions during dreams, often called “wet dreams,” occur in many males during some stages of sexual life, especially during the teenage years The male sexual act results from inherent reflex mechanisms integrated in the sacral and lumbar spinal cord, and these mechanisms can be initiated by either psychic stimulation from the brain or actual sexual stimulation from the sex organs, but usually it is a combination of both.

Question 26

Penile Erection—Role of the | Parasympathetic Nerves

Answer 26

Penile erection is the first effect of male sexual stimulation, and the degree of erection is proportional to the degree of stimulation, whether psychic or physical. Erection is caused by parasympathetic impulses that pass from the sacral portion of the spinal cord through the pelvic nerves to the penis. These parasympathetic nerve fibers, release nitric oxide and/or vasoactive intestinal peptide in addition to acetylcholine. Nitric oxide activates the enzyme guanylyl cyclase, causing increased formation of cyclic guanosine monophosphate (GMP). The cyclic GMP especially relaxes the arteries of the penis and the trabecular meshwork of smooth muscle fibers in the erectile tissue (corpora cavernosa and corpus spongiosum) in the shaft of the penis. As the vascular smooth muscles relax, blood flow into the penis increases, causing release of nitric oxide from the vascular endothelial cells and further vasodilation.

Question 27

Emission and Ejaculation Are Functions | of the Sympathetic Nerves.

Answer 27

 Filling of the internal urethra with semen elicits sensory signals that are transmitted through the pudendal nerves to the sacral regions of the cord, giving the feeling of sudden fullness in the internal genital organs.  Sensory signals further excite rhythmical contractions that increases pressure in both the erectile tissue of the penis and the genital ducts and urethra, which “ejaculate” the semen from the urethra to the exterior.  This final process is called ejaculation.  This entire period of emission and ejaculation is called the male orgasm.  At its termination, the male sexual excitement disappears almost entirely within 1 to 2 minutes and erection ceases, a process called resolution.

Question 28

Emission and Ejaculation Are Functions of the Sympathetic Nerves: Emission

Answer 28

Emission and ejaculation are the culmination of the male sexual act. When the sexual stimulus becomes extremely intense, the reflex centers of the spinal cord begin to emit sympathetic impulses that leave the cord at Thoracic vertebrae 12 to Lumbar vertebrae 2 and pass to the genital organs through the hypogastric and pelvic sympathetic nerve plexuses to initiate emission, the forerunner of ejaculation. Emission begins with contraction of the vas deferens and the ampulla to cause expulsion of sperm into the internal urethra. Then, contractions of the prostate gland followed by contraction of the seminal vesicles expel prostatic and seminal fluid also into the urethra, forcing the sperm forward. All these fluids mix in the internal urethra with mucus already secreted by the bulbourethral glands to form the semen. The process to this point is emission.

Question 29

Emission and Ejaculation Are Functions of the Sympathetic Nerves: Ejaculation

Answer 29

Filling of the internal urethra with semen elicits sensory signals that are transmitted through the pudendal nerves to the sacral regions of the cord, giving the feeling of sudden fullness in the internal genital organs. Sensory signals further excite rhythmical contractions that increases pressure in both the erectile tissue of the penis and the genital ducts and urethra, which “ejaculate” the semen from the urethra to the exterior. This final process is called ejaculation. This entire period of emission and ejaculation is called the male orgasm. At its termination, the male sexual excitement disappears almost entirely within 1 to 2 minutes and erection ceases, a process called resolution.

Question 30

Testosterone and Other Male Sex | Hormones

Answer 30

The testes secrete several male sex hormones, which are collectively called androgens, including testosterone, dihydrotestosterone, and androstenedione. The term “androgen” means any steroid hormone that has masculinizing effects, including testosterone; Testosterone is so much more abundant than the others that one can consider it to be the primary testicular hormone. Testosterone is formed by the interstitial cells of Leydig, which lie in the interstices between the seminiferous tubules and constitute about 20 percent of the mass of the adult testes. Leydig cells are almost non-existent in the testes during childhood when the testes secrete almost no testosterone, but they are numerous in the newborn male infant for the first few months of life and in the adult male after puberty; at both these times the testes secrete large quantities of testosterone.

Question 31

Functions of Testosterone

Answer 31

Testosterone is responsible for the distinguishing characteristics of the masculine body. During fetal life, the testes are stimulated by chorionic gonadotropin from the placenta to produce moderate quantities of testosterone throughout the entire period of fetal development and for 10 or more weeks after birth. Thereafter, essentially no testosterone is produced during childhood until about the ages of 10 to 13 years. Testosterone production then increases rapidly under the stimulus of anterior pituitary gonadotropic hormones at the onset of puberty and lasts throughout most of the remainder of life

Question 32

Functions of Testosterone During Fetal | Development

Answer 32

Testosterone begins to be elaborated by the male fetal testes at about the seventh week of embryonic life. The male sex chromosome has the sex-determining region Y (SRY) gene that encodes a protein called the testis determining factor (also called the SRY protein ). The SRY protein initiates a cascade of gene activations that cause the genital ridge cells to differentiate into cells that secrete testosterone and eventually become the testes. Testosterone secreted first by the genital ridges and later by the fetal testes is responsible for the development of the male body characteristics, including the formation of a penis and a scrotum rather than formation of a clitoris and a vagina. It also causes formation of the prostate gland, seminal vesicles, and male genital ducts, while at the same time suppressing the formation of female genital organs.

Question 33

Effect of Testosterone on Development of Adult Primary and Secondary Sexual Characteristics

Answer 33

After puberty, increasing amounts of testosterone secretion cause the penis, scrotum, and testes to enlarge about eightfold before the age of 20 years. In addition, testosterone causes the secondary sexual characteristics of the male to develop, beginning at puberty and ending at maturity. These secondary sexual characteristics, in addition to the sexual organs themselves, distinguish the male from the female as follows.

Question 34

Effect on the Distribution of Body Hair.

Answer 34

Testosterone causes growth of hair: 1. Over the pubis 2. Upward along the linea alba of the abdomen sometimes to the umbilicus and above, 3. On the face 4. Usually on the chest 5. Less often on other regions of the body, such as the back. It also causes the hair on most other portions of the body to become more prolific.

Question 35

Male Pattern Baldness.

Answer 35

Testosterone decreases the growth of hair on the top of the head; a man who does not have functional testes does not become bald. However, many virile men never become bald because baldness is a result of two factors: first, a genetic background for the development of baldness and, second, superimposed on this genetic background, large quantities of androgenic hormones.

Question 36

Testosterone Increases Protein Formation | and Muscle Development.

Answer 36

One of the most important male characteristics is development of increasing musculature after puberty, averaging about a 50 percent increase in muscle mass over that in the female. This increase in muscle mass is associated with increased protein in the nonmuscle parts of the body as well. Because of the great effect that testosterone and other androgens have on the body musculature, synthetic androgens are widely used by athletes to improve their muscular performance.

Question 37

Testosterone Increases Red Blood Cells.

Answer 37

When normal quantities of testosterone are injected into a castrated adult, the number of red blood cells per cubic millimeter of blood increases 15 to 20 percent. Despite the strong association of testosterone and increased hematocrit, testosterone does not appear to directly increase erythropoietin levels or have a direct effect on red blood cell production. The effect of testosterone to increase red blood cell production may be at least partly indirect because of the increased metabolic rate that occurs after testosterone administration.

Question 38

Production of Estrogen in the Male

Answer 38

In addition to testosterone, small amounts of estrogens are formed in the male. The exact source of estrogens in the male is unclear, but the following information is known: 1. The concentration of estrogens in the fluid of the seminiferous tubules is quite high and probably plays an important role in spermiogenesis. This estrogen is believed to be formed by the Sertoli cells by converting testosterone to estradiol. 2. Much larger amounts of estrogens are formed from testosterone and androstanediol in other tissues of the body, especially the liver, probably accounting for as much as 80 percent of the total male estrogen production.

Question 39

Abnormalities of the Male Sexual Function

Answer 39

Prostate Cancer Hypogonadism Testicular Tumours Erectile Dysfunction

Question 40

The Prostate Gland and Its Abnormalities

Answer 40

The prostate gland remains relatively small throughout childhood and begins to grow at puberty under the stimulus of testosterone. This gland reaches an almost stationary size by the age of 20 years and remains at this size up to the age of about 50 years. At that time, in some men it begins to involute, along with decreased production of testosterone by the testes

Question 41

Hypogonadism

Answer 41

Testes of the male are non-functional during the fetal life meaning that non of the male sexual characteristics develop in the fetus. The reason for this is the basic genetic characteristic of the fetus,whether it may be male or female is to form female sexual organs if the are no sex hormones present. However in the presence of testosterone the formation of female sexual organs is suppressed and male organs are induced instead. Causes of Hypogonadism: -Genetic inability of the hypothalamus to secrete normal amounts of GnRH- this condition is often ass, with a simultaneously abnormality of the feeding centre of the hypothalamus, causing a person to greatly overeat.-consequently obesity occurs with eunuchism The condition is called: - Adiposogenital Syndrome - Frohlich Syndrome - Hypothalamic Eunuchism !!!!!Do no forget to read about the part whereby a boy/man gets castrated and the effects of losing your teeth prior to puberty!!!!!!

Question 42

Testicular Tumors

Answer 42

Interstitial Leydig cell tumors develop in rare instances in the testes. These tumors sometimes produce as much as 100 times the normal quantities of testosterone. When such tumors develop in young children, they cause rapid growth of the musculature and bones but also early uniting of the epiphyses, so that the eventual adult height is actually considerably less than that which would have been achieved otherwise. Such interstitial cell tumors also cause excessive development of the male sexual organs, all skeletal muscles, and other male sexual characteristics.

Question 43

Erectile Dysfunction in the Male

Answer 43

Erectile dysfunction, also called “impotence,” is characterized by an inability of the man to develop or maintain an erection of sufficient rigidity for satisfactory sexual intercourse. Trauma to the parasympathetic nerves from prostate surgery, deficient levels of testosterone, and some drugs (e.g., nicotine, alcohol, and antidepressants) can also contribute to erectile dysfunction. Vascular disease, which can occur as a result of uncontrolled hypertension, diabetes, and atherosclerosis, reduces the ability of the body's blood vessels, including those in the penis, to dilate. Part of this impaired vasodilation is due to decreased release of nitric oxide.